The invention relates to a power generator, including a transformer with a primary winding arrangement and a secondary winding arrangement which is inductively coupled thereto, the primary winding arrangement forming a resonant circuit in conjunction with a capacitor, and a load being connected to the secondary winding arrangement. A "power generator" is to be understood to mean herein a generator capable of handling powers occurring in an X-ray generator for supplying filament current and high voltage to an X-ray tube. For filament current supply from 50 W to a few 100 W are then required, whereas generating the high voltage, (between 20 and 150 kV) requires powers of from 3 kW to more than 100 kW.
1. Description of the Related Art
A power generator of this kind, comprising a transformer without a ferromagnetic core, is known from EP-B2-141 985. It serves to generate high voltages in an X-ray generator. Its primary winding is connected in series with a direct voltage source and a switching device, a capacitor being connected parallel to the primary winding or the switching device. The switching device is periodically opened and closed, thus causing an approximately sawtooth-shaped current in the primary winding. In order to maximize the power transferred to the load and to minimize the energy fed back into the direct voltage source, inter alia the leakage inductance must be as small as possible or an as strong as possible inductive coupling should exist between the primary winding and the secondary winding. This requirement is very difficult to satisfy in the case of a high voltage transformer without an iron core, because the distance between the primary and the secondary winding must be as small as possible; on the other hand, a given minimum distance must be maintained between these components, as otherwise the high voltage strength is degraded.
Moreover, U.S. Pat. No. 3,596,167 describes a high voltage generator for an X-ray generator which comprises a plurality of cascade-connected transformers without a (closed) iron core. The transformers are coupled to one another via capacitive networks.